The present invention relates to a method for sampling a sensor that receives a pressure signal, the pressure signal being used as a basis for a pressure signal-based cylinder charge calculation for calculating a fresh-gas charge of a cylinder of an internal combustion engine.
When using sampling methods for sensor-supported, pressure-based charge determination, a pressure sensor may be sampled every 1 ms, and the sampled values may be subsequently added over a segment. The sum of the sampled values may be divided by the number of samplings, so that an arithmetic average is obtained that may permit a charge calculation on the basis of each partial pressure of residual gas and fresh gas of a cylinder of an internal combustion engine.
A pressure sensor that senses pressure signals may be sampled continuously every 1 ms, and an averaging may subsequently be performed between two firings (segment). The obtained values may be used to determine the total partial pressure, which consists of the partial residual-gas pressure and the partial fresh-gas pressure. Determining the total partial pressure and the charge that is dependent thereon at the individual cylinders of an internal combustion engine may only yield accurate values when the pulsation amplitude is symmetrical, to carry out a charge determination calculated indirectly by the induction-manifold pressure. In practice, the pulsation shapes that may occur at the instant at which the intake valve closes may be extremely unsymmetrical. Thus, an arithmetic averaging to determine the fresh-gas charge in the cylinder may produce inaccurate results. Due to sporadically occurring interferences, sampling every 1 ms may be significantly more sensitive than averaging. These interferences may be caused, for example, by electromagnetic influences (EMC). Such an electrical interference pulse may occur, for example, during a cold start and may corrupt the measuring result of the pressure sensor, thereby yielding an inaccurate charge calculation for the cylinder of the internal combustion engine. This may result in bad cold start performance, as well as a significant, yet avoidable, increase in emissions during the starting phase, which may seriously pollute the environment.
As a result of interfering pulses, such as, for example, those occurring during a cold start or those due to EMC influences, sampling the pressure sensor every 1 ms may result in incorrect pressure information for the fresh-gas charge calculation, since the determined partial pressures may be inaccurate and the actual conditions may not be correctly represented.
With an exemplary embodiment and/or exemplary method according to the present invention, the total partial pressure at the individual cylinders of an internal combustion engine may be measured multiple times in succession, shortly prior to the instant when the xe2x80x9cintake valve closesxe2x80x9d (ES) . The sampled values are divided by the number of samplings and a representative average pressure reflecting the actual conditions may be, consequently, available for further processing. The fresh-gas charge in the cylinder may be calculated on the basis of a representative average pressure determined in such a manner. As a result of the increased number of samplings of the pressure at the instant at which the xe2x80x9cintake valve closesxe2x80x9d (ES), the induction-manifold pressure, determined in the induction manifold of the internal combustion engine, corresponds to the total partial pressure prevailing in the cylinder. Since a large number of samplings may be performed in quick succession, during the abovementioned time, potential false samplings caused by EMC or other interfering pulses during the cold starting phase may be disregarded, so that inaccurate and corrupted pressure information will not enter the fresh-gas charge calculation.
It is believed that an advantage of an exemplary embodiment and/or exemplary method of the present invention involves the fact that, in engines having a large ratio of cylinder/induction manifold volumes (that is, in the case of an extremely small induction manifold), the damping effect of the induction manifold with regard to intake-air pulsations may be greatly reduced. A fresh-gas calculation using the induction-manifold pressure may not be possible in this case, since, in a steady state, the pressure signal exhibits pulsations that may be too great.